1. Field of the Invention
The present invention relates to method and apparatus for treating waste liquids containing body fluids so as to prevent problems such as nosocomial infection due to such waste liquids containing body fluids discharged from patients under (surgical) operation or treatment, particularly those waste liquids containing blood or irrigation liquid used to irrigate the body cavity of such patient.
2. Discussion of the Background
Nosocomial infection currently at issue in Japan has rapidly become a serious problem with the medical progress in the last dozen of years. Infection to compromised patients and occupational infection to persons engaged in medical treatments are particularly problematic.
Although the nosocomial infection occurs in various ways, secondary infection from a waste liquid containing body fluids, particularly blood, an irrigation liquid (isotonic sodium chloride solution) used to irrigate the body cavity, or a like fluid, discharged from a patient under surgical operation or treatment (hereinafter termed "waste liquid" for simplicity) to surroundings including personnel engaged in medical treatments and other patients is a serious problem. In 1989 the Japanese Welfare Ministry issued "Guideline for disposal of medical wastes" as a measure to prevent the nosocomial infection. According to the Guideline, all bloods and blood-adhering matters should be regarded as infectious industrial waste and should be subjected to incineration disposal or entrusted to professionals of waste disposal after they have been sterilized or disinfected.
The waste liquid usually contains a body cavity irrigation liquid in a considerable amount. This imposes a great expense on hospitals for treating the waste liquid.
Various proposals have been made to overcome this situation.
Collecting bottles, for example, have conventionally been used as waste liquid treating containers. Such collecting bottles generally are relatively heavy and easy to break and, hence, dangerous to persons handling the bottles. In addition, there are required time and labor for disinfecting or sterilizing an infectious waste liquid before its disposal and for washing used bottles later. In view of this, containers of synthetic resin have become employed. Since such containers are less expensive and lighter than the collecting bottles and, in addition, are disposable, it becomes possible to dispose of collected waste liquids together with their containers. This eliminates the operations previously required to dispose of only waste liquids and wash the inside of bottles (refer to, for example, Japanese Unexamined Patent Publication No. SHO 51-48589).
However, the amount of waste liquids to be disposed of remains unvaried though the weight of the container is reduced by replacing a collecting bottle with a container of synthetic resin. Further, if one tries to incinerate a waste liquid as contained in the container using the incineration facility of a hospital, the waste liquid undesirably flows down below the incinerator with its infectiousness maintained. Thus, such incineration is difficult. After all, the process of adding an expensive microbicide to the waste liquid and draining the resultant to a sewerage system must be carried out.
In view of the fact that the greater part of the content in such container is moisture (isotonic sodium chloride solution and the like other than body fluids), a method has been employed such that a water-absorptive flocculant is provided in a container to cause the waste liquid to solidify (refer to, for example, Japanese Examined Patent Publication No. HEI 4-60713).
Although this method enables the incineration of waste liquid, substantial time and thermal energy are required to complete the incineration of the waste liquid because the thermal conductivity of the solidified waste liquid is low due to solidification. Further, not a few hospitals cannot use their incineration facilities for fear that smoke emitted by incineration should flow to residential areas. Such hospitals and those having no incineration facility are required to entrust the disposal of waste liquids to professionals of disposal. Since the overall weight of a container containing solidified waste liquid is not different from that of the foregoing container containing not solidified waste liquid, the proportion of the costs of entrusting the disposal of waste liquids in the total expenditure of a hospital is substantially high and, hence, the financial management of the hospital is oppressed.
To solve this problem, a waste liquid treating method has been proposed which is adapted to eliminate the moisture of waste liquid (refer to, for example, Japanese Examined Patent Publication No. HEI 6-36813). This prior art waste liquid treating method described in Publication No. HEI 6-36813 comprises collecting a waste liquid into a storage container by suction, eliminating the moisture of the waste liquid through a filter which is capable of filtering off infectious microbes, and disposing of the storage container having infectious microbes of the waste liquid together with the filter. This method markedly reduces the total weight and volume of the waste including the container to be disposed of as compared to the method previously described, thereby facilitating the incineration of the waste. Further, this method causes the container itself to shrink, the cost of entrusting the disposal, which depends on the weight and volume of the waste to be disposed of, can be reduced.
Japanese Unexamined Patent Publication No. HEI 1-96558 discloses another prior art technique wherein "in disposing of blood in hospitals a flocculant is added to a waste liquid to be disposed of, and the resulting mixture is stirred thereby causing almost all the blood components to flocculate".
The prior art described in Japanese Examined Patent Publication No. HEI 6-36813, however, has drawbacks that the filter may be clogged to become incapable of eliminating the moisture since microbes such as viruses, bacteria and Eumycetes existing in an infectious waste liquid are smaller than coexisting protein components such as red blood cells, that the container does not shrink as the case may be, and that the container including the filter becomes costly since the filter is expensive.
The prior art described in Japanese Unexamined Patent Publication No. HEI 1-96558 does not disclose any specific process to be performed after the separation of the waste liquid into a supernatant liquor (water content) and a flocculate (protein) and, hence, it is unclear how to treat the supernatant liquor and the flocculate for their disposal. Thus, this art is difficult to practically apply to disposal of infectious wastes. In brief this prior art merely discloses a method of separating a waste liquid, but does not disclose a method of treating the waste liquid for subjecting it to disposal.